Add __init__.py to NRT tests

Author: gmarkall

numba_cuda/numba/cuda/tests/nrt/__init__.py

@@ -0,0 +1,8 @@
+from numba.cuda.testing import ensure_supported_ccs_initialized
+from numba.cuda.tests import load_testsuite
+import os
+
+
+def load_tests(loader, tests, pattern):
+    ensure_supported_ccs_initialized()
+    return load_testsuite(loader, os.path.dirname(__file__))